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Message-ID: <2aa4bfd4-b7ce-4b00-b21e-781936c4a0fd@samsung.com>
Date: Tue, 17 Sep 2024 04:24:00 +0530
From: Selvarasu Ganesan <selvarasu.g@...sung.com>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
Cc: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"jh0801.jung@...sung.com" <jh0801.jung@...sung.com>, "dh10.jung@...sung.com"
<dh10.jung@...sung.com>, "naushad@...sung.com" <naushad@...sung.com>,
"akash.m5@...sung.com" <akash.m5@...sung.com>, "rc93.raju@...sung.com"
<rc93.raju@...sung.com>, "taehyun.cho@...sung.com"
<taehyun.cho@...sung.com>, "hongpooh.kim@...sung.com"
<hongpooh.kim@...sung.com>, "eomji.oh@...sung.com" <eomji.oh@...sung.com>,
"shijie.cai@...sung.com" <shijie.cai@...sung.com>
Subject: Re: [PATCH] usb: dwc3: Potential fix of possible dwc3 interrupt
storm
On 9/17/2024 2:48 AM, Thinh Nguyen wrote:
> On Mon, Sep 16, 2024, Selvarasu Ganesan wrote:
>> On 9/13/2024 11:21 PM, Thinh Nguyen wrote:
>>> Hi,
>>>
>>> On Fri, Sep 13, 2024, Selvarasu Ganesan wrote:
>>>> Hi Thinh,
>>>>
>>>> So far, there have been no reported error instances. But, we suspecting
>>>> that the issue may be related to our glue driver. In our glue driver, we
>>>> access the reference of evt->flags when starting or stopping the gadget
>>>> based on a VBUS notification. We apologize for sharing this information
>>>> so late, as we only became aware of it recently.
>>>>
>>>> The following sequence outlines the possible scenarios of race conditions:
>>>>
>>>> Thread#1 (Our glue Driver Sequence)
>>>> ===================================
>>>> ->USB VBUS notification
>>>> ->Start/Stop gadget
>>>> ->dwc->ev_buf->flags |= BIT(20); (It's for our reference)
>>>> ->Call dwc3 exynos runtime suspend/resume
>>>> ->dwc->ev_buf->flags &= ~BIT(20);
>>>> ->Call dwc3 core runtime suspend/resume
>>>>
>>>> Thread#2
>>>> ========
>>>> ->dwc3_interrupt()
>>>> ->evt->flags |= DWC3_EVENT_PENDING;
>>>> ->dwc3_thread_interrupt()
>>>> ->evt->flags &= ~DWC3_EVENT_PENDING;
>>>>
>>> This is great! That's likely the problem. Glad you found it.
>>>
>>>> After our internal discussions, we have decided to remove the
>>>> unnecessary access to evt->flag in our glue driver. We have made these
>>>> changes and initiated testing.
>>>>
>>>> Thank you for your help so far to understand more into our glue driver code.
>>>>
>>>> And We are thinking that it would be fine to reset evt->flag when the
>>>> USB controller is started, along with the changes you suggested earlier.
>>>> This additional measure will help prevent similar issues from occurring
>>>> in the future.
>>>>
>>>> Please let us know your thoughts on this proposal. If it is not
>>>> necessary, we understand and will proceed accordingly.
>>>>
>>> You can submit the change I suggested. That's a valid change. However,
>>> we should not include the reset of the DWC3_EVENT_PENDING flag. Had we
>>> done this, you may not found the issue above. It serves no purpose for
>>> the core driver logic and will be an extra burden for us to maintain. (I
>>> don't want to scratch my head in the future to figure out why that
>>> change was needed or concern whether it can be removed without causing
>>> regression).
>> Yeah I understand.
>>
>> Please reconfirm the below changes once with commit message. I will post
>> new version if this changes are fine.
>>
>>
>> [PATCH] usb: dwc3: core: Stop processing of pending events if controller
>> is halted
>>
>> This commit addresses an issue where events were being processed when
>> the controller was in a halted state. To fix this issue by stop
>> processing the events as the event count was considered stale or
>> invalid when the controller was halted.
>>
>> Fixes: fc8bb91bc83e ("usb: dwc3: implement runtime PM")
>> Cc: stable <stable@...nel.org>
>> Signed-off-by: Selvarasu Ganesan <selvarasu.g@...sung.com>
>> Suggested-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
>> ---
>> drivers/usb/dwc3/core.c | 17 +++++++++++++++--
>> drivers/usb/dwc3/core.h | 4 ----
>> drivers/usb/dwc3/gadget.c | 22 +++++++++++-----------
>> 3 files changed, 26 insertions(+), 17 deletions(-)
>>
>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>> index 9eb085f359ce..f47b20bc2d1f 100644
>> --- a/drivers/usb/dwc3/core.c
>> +++ b/drivers/usb/dwc3/core.c
>> @@ -544,6 +544,7 @@ static int dwc3_alloc_event_buffers(struct dwc3
>> *dwc, unsigned int length)
>> int dwc3_event_buffers_setup(struct dwc3 *dwc)
>> {
>> struct dwc3_event_buffer *evt;
>> + u32 reg;
>>
>> if (!dwc->ev_buf)
>> return 0;
>> @@ -556,8 +557,10 @@ int dwc3_event_buffers_setup(struct dwc3 *dwc)
>> upper_32_bits(evt->dma));
>> dwc3_writel(dwc->regs, DWC3_GEVNTSIZ(0),
>> DWC3_GEVNTSIZ_SIZE(evt->length));
>> - dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), 0);
>>
>> + /* Clear any stale event */
> Do the same thing here as in dwc3_event_buffers_cleanup().
done in new version.
>
>> + reg = dwc3_readl(dwc->regs, DWC3_GEVNTCOUNT(0));
>> + dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), reg);
>> return 0;
>> }
>>
>> @@ -2499,7 +2502,11 @@ static int dwc3_runtime_resume(struct device *dev)
>>
>> switch (dwc->current_dr_role) {
>> case DWC3_GCTL_PRTCAP_DEVICE:
>> - dwc3_gadget_process_pending_events(dwc);
>> + if (dwc->pending_events) {
>> + pm_runtime_put(dwc->dev);
>> + dwc->pending_events = false;
>> + enable_irq(dwc->irq_gadget);
>> + }
>> break;
>> case DWC3_GCTL_PRTCAP_HOST:
>> default:
>> @@ -2589,6 +2596,12 @@ static void dwc3_complete(struct device *dev)
>> static const struct dev_pm_ops dwc3_dev_pm_ops = {
>> SET_SYSTEM_SLEEP_PM_OPS(dwc3_suspend, dwc3_resume)
>> .complete = dwc3_complete,
>> +
>> + /*
>> + * Runtime suspend halts the controller on disconnection. It
>> replies on
>> + * platforms with custom connection notification to start the
>> controller
>> + * again.
>> + */
>> SET_RUNTIME_PM_OPS(dwc3_runtime_suspend, dwc3_runtime_resume,
>> dwc3_runtime_idle)
>> };
>> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
>> index c71240e8f7c7..9c508e0c5cdf 100644
>> --- a/drivers/usb/dwc3/core.h
>> +++ b/drivers/usb/dwc3/core.h
>> @@ -1675,7 +1675,6 @@ static inline void dwc3_otg_host_init(struct dwc3
>> *dwc)
>> #if !IS_ENABLED(CONFIG_USB_DWC3_HOST)
>> int dwc3_gadget_suspend(struct dwc3 *dwc);
>> int dwc3_gadget_resume(struct dwc3 *dwc);
>> -void dwc3_gadget_process_pending_events(struct dwc3 *dwc);
>> #else
>> static inline int dwc3_gadget_suspend(struct dwc3 *dwc)
>> {
>> @@ -1687,9 +1686,6 @@ static inline int dwc3_gadget_resume(struct dwc3 *dwc)
>> return 0;
>> }
>>
>> -static inline void dwc3_gadget_process_pending_events(struct dwc3 *dwc)
>> -{
>> -}
>> #endif /* !IS_ENABLED(CONFIG_USB_DWC3_HOST) */
>>
>> #if IS_ENABLED(CONFIG_USB_DWC3_ULPI)
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index 291bc549935b..a32c3a292353 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -4483,6 +4483,17 @@ static irqreturn_t dwc3_check_event_buf(struct
>> dwc3_event_buffer *evt)
>> return IRQ_HANDLED;
>>
>> count = dwc3_readl(dwc->regs, DWC3_GEVNTCOUNT(0));
> If we properly cleanup event count in dwc3_event_buffers_cleanup() as
> noted above, then you don't need this condition below. You can remove
> the below check:
done in new version.
>
>> +
>> + /*
>> + * If the controller is halted, the event count is
>> stale/invalid. Ignore
>> + * them. This happens if the interrupt assertion is from an
>> out-of-band
>> + * resume notification.
>> + */
>> + if (!dwc->pullups_connected && count) {
>> + dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), count);
>> + return IRQ_HANDLED;
>> + }
>> +
>> count &= DWC3_GEVNTCOUNT_MASK;
>> if (!count)
>> return IRQ_NONE;
>> @@ -4728,14 +4739,3 @@ int dwc3_gadget_resume(struct dwc3 *dwc)
>>
>> return dwc3_gadget_soft_connect(dwc);
>> }
>> -
>> -void dwc3_gadget_process_pending_events(struct dwc3 *dwc)
>> -{
>> - if (dwc->pending_events) {
>> - dwc3_interrupt(dwc->irq_gadget, dwc->ev_buf);
>> - dwc3_thread_interrupt(dwc->irq_gadget, dwc->ev_buf);
>> - pm_runtime_put(dwc->dev);
>> - dwc->pending_events = false;
>> - enable_irq(dwc->irq_gadget);
>> - }
>> -}
Hi Thinh,
Thanks for your suggestions. I posted a updated version in the below
link. SO, kindly review the same.
https://lore.kernel.org/lkml/20240916224543.187-1-selvarasu.g@samsung.com/
Thanks,
Selva
> The rest looks fine.
>
> Thanks,
> Thinh
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